.TH HTTPD 8
.SH NAME
httpd, mirror, save, imagemap, man2html, webls \- HTTP server
.SH SYNOPSIS
.B ip/httpd/httpd
.RB [ -a
.IR srvaddr ]
.RB [ -c
.IR cert ]
.RB [ -d
.IR domain ]
.RB [ -n
.IR namespace ]
.RB [ -w
.IR webroot ]
.PP
.B ip/httpd/mirror
.RB [ -b
.IR inbuf ]
.RB [ -d
.IR domain ]
.RB [ -r
.IR remoteip ]
.RB [ -w
.IR webroot ]
.RB [ -N
.IR netdir ]
.I method version uri
.RI [ search ]
.PP
.B ip/httpd/save
.RB [ -b
.IR inbuf ]
.RB [ -d
.IR domain ]
.RB [ -r
.IR remoteip ]
.RB [ -w
.IR webroot ]
.RB [ -N
.IR netdir ]
.I method version uri
.RI [ search ]
.PP
.B ip/httpd/imagemap
.RB [ -b
.IR inbuf ]
.RB [ -d
.IR domain ]
.RB [ -r
.IR remoteip ]
.RB [ -w
.IR webroot ]
.RB [ -N
.IR netdir ]
.I method version uri
.PP
.B ip/httpd/man2html
.RB [ -b
.IR inbuf ]
.RB [ -d
.IR domain ]
.RB [ -r
.IR remoteip ]
.RB [ -w
.IR webroot ]
.RB [ -N
.IR netdir ]
.I method version uri
.RI [ search ]
.PP
.B ip/httpd/webls
.RB [ -b
.IR inbuf ]
.RB [ -d
.IR domain ]
.RB [ -r
.IR remoteip ]
.RB [ -w
.IR webroot ]
.RB [ -N
.IR netdir ]
.I method version uri
.RI [ search ]
.SH DESCRIPTION
.I Httpd
serves the
.I webroot
directory of the file system described by
.I namespace
(default
.BR /lib/namespace.httpd ),
using version 1.1 of the HTTP protocol.
It announces the service
.I srvaddr
(default
.BR tcp!*!http ),
and listens for incoming calls.
If an X.509 certificate is supplied with the
.B -c
option, then the service is instead
.BR tcp!*!https .
There should already be a factotum
holding the corresponding private key.
.PP
.I Httpd
supports only the GET and HEAD methods of the HTTP protocol;
some magic programs support POST as well.
Persistent connections are supported for HTTP/1.1 or later clients;
all connections close after a magic command is executed.
The Content-type
(default
.BR application/octet-stream )
and Content-encoding
(default
.BR binary )
of a file are determined by looking for suffixes of the file name in
.BR /sys/lib/mimetype .
.SS Redirection
.PP
Each requested URI is looked up in a redirection table, read from
.BR /sys/lib/httpd.rewrite .
Fields are separated by spaces and tabs.
Anything following a
.L #
is ignored.
The first field of each line is a URI;
the second a replacement path.
If a prefix of the URI matches a redirection path,
the URI is rewritten using the corresponding replacement path
instead of the prefix,
and a temporary redirect is sent to the HTTP client.
If the replacement path does not specify a server name,
and the request has no explicit host,
then
.I domain
is the host name used in the redirection.
The prefix can either be a domain root like
.B http://system/
(which matches that URL only)
or a path like
.B /who/rob
(which matches that path no matter what
the requested server),
but not both:
.B http://system/who/rob
will never match a request.
If the first field ends in a slash, this is an exact match;
otherwise it is a prefix match.
The first field is a literal string, matched against
each file prefix of each URL.
The most specific, i.e., longest,
pattern wins, and is applied once (there is no rescanning),
except for the following exceptions.
.I Httpd
matches only the prefix and not subordinate pages
if a replacement is prefixed with 
.LR > .
.I Httpd
omits the unmatched part of the original URI
from the rewritten URI if the replacement is prefixed with 
.LR * .
This permits many-to-one mappings; for example,
to send all references to an old subtree to a single error page.
.PP
.I Httpd
handles replacements prefixed with 
.L @ 
internally,
treating the request as if it were for the replacement
(without the
.BR @ )
but not informing the client of the rewritten name.
Replacement URLs prefixed with 
.L =
generate a permanent redirection instead of a temporary one.
.I Httpd
checks to see if this file has changed once every 50 new TCP connections.
HTTP 1.1 persistent connection implies many pages
may come in one browser connection, so to kick-start
.IR httpd ,
try
.IP
.EX
for(i in `{seq 50}) hget http://www.your-domain.com/ >/dev/null
.EE
.SS "Access Control"
.PP
Before opening any file,
.I httpd
looks for a file in the same directory called
.BR .httplogin .
If the file exists, the directory is considered
locked and the client must specify a user name
and password matching a pair in the file.
.B .httplogin
contains a list of space or newline separated tokens, each
possibly delimited by single quotes.  The first
is a domain name presented to the HTTP client.
The rest are pairs of user name and password.
Thus, there can be many user name/password pairs
valid for a directory.
.br
.ne 3
.SS "Auxiliaries (magic)"
.PP
If the requested URI begins with
.BI  /magic/ server /\f1,
.I httpd
executes the file
.BI /bin/ip/httpd/ server
to finish servicing the request.
.IR Method
and
.IR version
are those received on the first line of the request.
.I Uri
is the remaining portion of the requested URI.
.I Inbuf
contains the rest of the bytes read by the server,
and
.I netdir
is the network directory for the connection.
There are routines for processing command arguments,
parsing headers, etc. in the httpd library,
.BR /sys/src/cmd/ip/httpd/libhttpd.a.$O .
See
.B httpd.h
in that directory and existing magic commands for more details.
.PP
.I Mirror
is a trivial server that just returns the method, URI, any search,
the headers, and the message body sent by the client.
.PP
.I Save
writes a line to
.BI /usr/web/save/ uri .data
and returns the contents of
.BI /usr/web/save/ uri .html.
Both files must be accessible for the request to succeed.
The saved line includes the current time
and either the search string from a HEAD or GET
or the first line of the body from a POST.
It is used to record form submissions.
.PP
.I Imagemap
processes an HTML imagemap query.
It looks up a the point
.I search
in the image map file given by 
.IR uri ,
and returns a redirection to the appropriate page.
The map file defaults to NCSA format.
Any entries after a line starting with the word
.B #cern
are interpreted in CERN format.
.PP
.I Man2html
converts
.IR man (6)
format manual pages into html.
It includes some abilities to search the manuals.
.PP
.I Webls
produces directory listings on the fly, with
output in the style of
.IR ls (1).
.B /sys/lib/webls.allowed
and
.B /sys/lib/webls.denied
contain regular expressions describing
what parts of
.I httpd's
namespace may and may not be listed, respectively.
.B Webls.denied
is first searched to see if access is by default
denied.  If so
.B webls.allowed
is then searched to see if access is explicitly allowed.
Thus one can have very general expressions in the
denied list (like
.BR .* ),
yet still allow exceptions.  If
.B webls.denied
does not exist or is unreadable, 
all accesses are assumed to be denied unless
explicitly allowed in
.B webls.allowed.
.PP
Other sites will note that if neither
.B webls.denied
nor
.B webls.allowed
exist, any portion of
.I httpd's
namespace can be listed (however,
.I webls
will always endeavor to prevent listing of `.' and `..').
If
.B webls.allowed
exists but
.B webls.denied
does not, any directory to be listed must be described
by a regular expression in
.BR webls.allowed .
Similarly, if
.B webls.denied
exists but
.B webls.allowed
does not, any directory to be listed must
.I not
be described by a regular expression in
.BR webls.denied .
If both exist, a directory is listable if either
it doesn't appear in
.BR webls.denied ,
or it appears in both
.B webls.denied
and
.BR webls.allowed .
In other words,
.B webls.allowed
overrides
.BR webls.denied .
If a listing for a directory is requested and access
is denied, or another error occurs, a simple error
page is returned.
.SH EXAMPLES
These are all examples of how to use
.BR httpd.rewrite .
.PP
A local redirection:
.RS
.EX
/netlib/c++/idioms/index.html.Z /netlib/c++/idioms/index.html
.EE
.RE
.PP
Redirection to another site:
.RS
.EX
/netlib/lapack/lawns		=http://netlib.org/lapack/lawns
http://inferno.bell-labs.com	=http://www.vitanuova.com
.EE
.RE
.PP
Root directory for virtual host:
.RS
.EX
http://www.ampl.com		/cm/cs/what/ampl
.EE
.RE
.SH FILES
.TF /sys/lib/httpd.rewrite
.TP
.B /sys/lib/mimetype
content type description file
.TP
.B /lib/namespace.httpd
default namespace file for httpd
.TP
.B /sys/lib/httpd.rewrite
redirection file
.TP
.B /sys/lib/webls.allowed
regular expressions describing explicitly listable pathnames; overrides
.B webls.denied
.TP
.B /sys/lib/webls.denied
regular expressions describing explicitly unlistable pathnames
.SH SOURCE
.B /sys/src/cmd/ip/httpd
.SH "SEE ALSO"
.I newns
in
.IR auth (2),
.IR listen (8),
.IR rsa (8)